Screw type extruders typically include a screw positioned for rotation in an extruder barrel. The extruders generally include three zones, namely a feed zone, a melting/softening zone, and a metering zone employed in the feeding, melting/softening and forming of a material such as an elastomeric material, respectively. An interior area of the extruder barrel and the surface of the screw define a channel therebetween through which the elastomeric material introduced to the feed zone is conveyed. Axial rotation of the screw causes the elastomeric material to be conveyed successively through the feed, melting/softening and metering zones. A shaping die is positioned on a discharge end of the extruder, adjacent to the metering zone for extruding the elastomeric material into a particular cross sectional configuration.
The feed zone typically includes a hopper extending therefrom and having an opening for introduction of the elastomeric materials into the hopper. The hopper has a bore extending therethrough and into which a portion of the screw extends. A drive mechanism is mounted to one side of the hopper and is rotatably coupled to the screw. In addition, a feed roll is positioned on a mounting frame in the hopper and is rotatably coupled to the drive mechanism. The feed roll rotates in a direction counter to the rotation of the extruder screw and creates a roll nip that pinches and impinges the elastomeric material into the feed zone of the screw. The screw then conveys the elastomeric material through the channel for extrusion through the shaping die.
During operation, the elastomeric material is caused to soften in the feed zone and progressively softens during conveyance through the channel. If operation of the extruder is interrupted while the softened elastomeric material is present in the hopper, the material could harden on the feed rolls and adjacent areas. Typically, a labor intensive disassembly is required to clean the hardened material from the feed rolls and the adjacent areas.